Methods and devices for electrophotographic printing

Abstract

A printing device includes a developer for developing a latent image with toner particles; an imaging plate comprising a plurality of pixel plates; and a plurality of voltage generators connected respectively to the pixel plates. The voltage generators positively bias selected pixel plates to form a latent image that is developed with toner from the developer. Another printing device includes a developer for developing a latent image with toner particles; an imaging plate comprising a plurality of pixel plates for selectively receiving toner particles from the developer; a plurality of voltage generators for biasing respective to pixel plates; and a background grid in the imaging plate for preventing toner particles from being deposited in areas between the pixel plates, wherein the background grid is connected to a voltage generator for applying a range of biases, positive and negative to the background grid. A method of electrophotographic printing in which toner particles are moved electrostatically from a developer to develop a latent image includes positively biasing selected pixel plates of a plurality of pixel plates of an imaging plate to form the latent image; and developing the latent image with the toner particles from the developer.

What is claimed is: 
     
       1. A printing device comprising:
 a developer for developing a latent image with toner particles; 
 an imaging plate comprising a plurality of pixel plates; and 
 a plurality of voltage generators connected respectively to said pixel plates; 
 wherein said voltage generators bias selected pixel plates to form a latent image that is developed with toner from said developer. 
 
     
     
       2. The device of  claim 1 , further comprising a voltage generator for biasing said developer to attract oppositely charged toner particles, wherein said voltage generators connected respectively to said pixel plates selectively bias said pixel plates to attract said oppositely charged toner particles, said pixel plates, when selectively biased, being biased more strongly than said developer. 
     
     
       3. The device of  claim 1 , further comprising a background grid in said imaging plate for preventing toner particles from being deposited in areas between said pixel plates. 
     
     
       4. The device of  claim 3 , wherein said background grid is connected to a voltage generator for applying a range of biases, positive and negative to said background grid. 
     
     
       5. The device of  claim 4 , further comprising a ground plate and a switch connected between said background grid and said voltage generator of said background grid such that, by operation of said switch, said background grid can be selectively connected either to a said voltage generator or said ground plate. 
     
     
       6. The device of  claim 3 , wherein said background grid is co-planar with said pixel plates. 
     
     
       7. The device of  claim 3 , wherein said background grid is sub-planar with respect to said pixel plates and located in an insulating layer of said imaging plate. 
     
     
       8. The device of  claim 3 , wherein said background grid comprises corbino rings. 
     
     
       9. The device of  claim 8 , wherein each said corbino ring is connected to a respective voltage generator for applying a range of biases, positive and negative to said respective corbino ring. 
     
     
       10. The device of  claim 1 , further comprising a media sensor and feeding device for feeding print media onto said imaging plate, wherein said developer develops said latent image directly on said print media. 
     
     
       11. The device of  claim 10 , wherein said media sensor is a capacitive sensor that includes a pixel plate of said imaging plate. 
     
     
       12. The device of  claim 1 , further comprising a ground plate and a plurality of switches connected between respective pixel plates and voltage generator such that, by operation of a said switch, each pixel plate can be selectively connected either to a said voltage generator or said ground plate. 
     
     
       13. A printing device comprising:
 a developer for developing a latent image with toner particles; 
 an imaging plate comprising a plurality of pixel plates for selectively receiving toner particles from said developer; 
 a plurality of voltage generators for biasing respective to pixel plates; and 
 a background grid in said imaging plate for preventing toner particles from being deposited in areas between said pixel plates, wherein said background grid is connected to a voltage generator for applying a range of biases, positive and negative to said background grid. 
 
     
     
       14. The device of  claim 13 , wherein said voltage generators connected to said pixel plates positively bias selected pixel plates to form a latent image that is developed with toner from said developer. 
     
     
       15. The device of  claim 13 , further comprising a voltage generator for positively biasing said developer. 
     
     
       16. The device of  claim 13 , further comprising a ground plate and a switch connected between said background grid and said voltage generator of said background grid such that, by operation of said switch, said background grid can be selectively connected either to a said voltage generator or said ground plate. 
     
     
       17. The device of  claim 13 , wherein said background grid is co-planar with said pixel plates. 
     
     
       18. The device of  claim 13 , wherein said background grid is sub-planar with respect to said pixel plates and located in an insulating layer of said imaging plate. 
     
     
       19. The device of  claim 13 , wherein said background grid comprises corbino rings. 
     
     
       20. The device of  claim 19 , wherein each said corbino ring is connected to a respective voltage generator for applying a range of biases, positive and negative to said respective corbino ring. 
     
     
       21. The device of  claim 19 , further comprising a media sensor and feeding device for feeding print media onto said imaging plate, wherein said developer develops said latent image directly on said print media. 
     
     
       22. A method of electrophotographic printing in which toner particles are moved electrostatically from a developer biased to attract oppositely charged toner particles to develop a latent image, said method comprising:
 biasing selected pixel plates of a plurality of pixel plates of an imaging plate to form said latent image, wherein said selected pixel plates are biased to attract oppositely charged toner particles, and said pixel plates, when selectively biased, are biased more strongly than said developer; and 
 developing said latent image with said toner particles from said developer. 
 
     
     
       23. The method of  claim 22 , further comprising positively biasing said developer. 
     
     
       24. The method of  claim 22 , further comprising preventing toner particles from being deposited in areas between said pixel plates with a background grid in said imaging plate. 
     
     
       25. The method of  claim 24 , wherein said background grid is connected to a voltage generator for applying a range of biases, positive and negative to said background grid. 
     
     
       26. The method of  claim 24 , wherein said background grid comprises corbino rings. 
     
     
       27. The method of  claim 22 , further comprising feeding print media onto said imaging plate, wherein said developer develops said latent image directly on said print media. 
     
     
       28. A system for electrophotographic printing in which toner particles are moved electrostatically from a developer biased to attract oppositely charged toner particles to develop a latent image, said system comprising:
 means for biasing selected pixel plates of a plurality of pixel plates of an imaging plate to form said latent image, wherein said selected pixel plates are biased to attract oppositely charged toner particles, and said pixel plates, when selectively biased, are biased more strongly than said developer; and 
 means for developing said latent image with said toner particles from said developer.